Something handmade. A cute crafty card would make me melt. Dinner is a great idea too.
I wouldn't go so far as to spend 20$ to 40$ on someone you haven't known that long, but hey...my first date with my boyfriend costed 70$+ because it was prom!
(Of course, that's because he ordered shrimp cocktail, a huge entree, and a big piece of chocolate cake...I stuck to some raviolis and water.)